Many kinds of flooring systems are known. In traditional tiling systems, a sub-floor is built on top of a structural base; a mortar material, sometimes termed a thinset, is applied and trowelled; the tiles are laid down; and grouting is applied. Sometimes a membrane is applied over the subfloor, and sometimes a membrane is applied between a first thinset layer and a second thinset layer. All of these are a labour intensive processes. Further, once laid, the tiles cannot be lifted and re-laid, or replaced, without great effort, and removal may tend to mean destruction of the tiles. In the past, it has been known to install porcelain tiles over a sub-floor. The subfloor is, typically, wooden, whether made of plywood (most commonly) or oriented strandboard (OSB). A membrane, typically a polymeric membrane or sheet, is laid over the sub-floor. The tiles are then laid on top of the membrane, then the grouting is applied. The cost of the flooring may be $8/sq.ft., and the cost of the installation may be $5-6/sq.ft.